Heating system



: March 20, 1934.

J. H. .VANI ZANDT I HEATING SYSTEM Fil-ed Jan. 2, 1929 4 Sheets-Sheet. l

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March 20, 1934.

J. H. VAN ZANDT HEATING SYSTEM Filed Jan. 2. 1929 4 Shgets-Shaet 2 ITMZTL'EF Mn 5/% @Z/Zdf J. H. VAN ZANDT 1,951,588

HEATING SYSTEM- Filed Jan. 2, 1929 4 sheets-sh et 3 March 20, 1934.

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Infant)? 70522 15 %22 Zena f March 20, 1934. J. H. VAN ZANDT 1,951,583

HEATING SYSTEM Filed Jan. 2, 1929 4 Sheets-Sheet 4 L Q $7 1 7 9 y 9 W m6 w W. w

lilll jjlllllllllll 100 E z ll Patented Mar. 20, 1934 HEATING SYSTEM John H. Van Zandt, Dallas, Ta, assignor to o. A.

Dunham Company, Marshalltown,

poration of Iowa Application January 2,

18 Claims.

This invention relates to certain improvements in a vacuum steam heating system comprising a plurality of independently controlled radiating units, and more particularly to improvements in a system adapted to operate with steam at controlled sub-atmospheric pressures, as disclosed in the patent to Dunham 1,644,114 granted October 4, 1927.

In a system of the type disclosed in this Dunham patent, steam is supplied under a vacuum, or at a sub-atmospheric pressure, to an evacuated condensing space or radiator. A reducing valve or generator-control mechanism, is'provided for regulating the sub-atmospheric pressure of the steam in the supply pipe and radiator. The pressure of the steam determines its temperature and consequently the amount of heat given out by the radiator. Areturr? main for withdrawing air and condensate from the radiatorleads 20 through a thermostatically controlled steam trap which prevents the escape of steam from the radiator. An exhausting mechanism operates on the return main to withdraw condensate and maintain the vacuum in the system. A differential pressure controller connected between the supply and return sides of .the system governs the operation of the exhausting means so as to maintain a substantially constant and predetermined difference in pressure between the supply and exhaust sides of the radiator no matter what the absolute pressure of the steam in the radiator may be. This pressure differential will be just suflicient to insure the withdrawal of air and condensate from the radiator so that the radiator will be maintained full of steam at all.-times.

In heating buildings in many sections of the country provision must be made to care for sudden and severe wind conditions, and other differences in external temperature conditions at opposite sides of a. building. For example, in certain localities there are times when high winds accompanied by falling temperatures come from the north. In such instances the north side of a budding is hard to heat whereas the other sides may be heated with relative ease. The internal structure and arrangements of the difierent portions of a building may also make certain sections of the building more diflicult to heat than others. In order to combat these conditions, it has been proposed to have separate and distinct heat'ng systems for the diflferent portions of a building, so that steam at a higher pressure and temperature can be supplied to the heating system in that portion of a building subjected to the more severe weather conditions, or

Iowa, a cor- 1929, Serial No. 329,806

for any other reason suffering greater heat losses, while lower pressure steam can be supplied to the system or systems in those portions of the bulding where less heat is required.

The general object of this invention is to provide a vacuum heating system of the type just described, involving two or more separate and distinct radiating or condensing systems for different parts 01" the building, all of the systems being supplied from the same source of steam, and a single exhausting mechanism being utilized to maintain the-requisite sub-atmospheric pressures and the desired pressure difierentials in each of the several systems.

Another object is to provide in combination with suchv a system means for starting the operation of the exhausting mechanism when the pressure differential in any one of the systems falls below a desired minimum, and for stopping the operation of theexhausting mechanism when v the desired pressure differential has been established in all of the systems.

Another object of the invention is to provide means for automatically making the exhausting mechanism, when in operation, efiective only in that individual radiating system or systems in which the desired pressure difierential has not yet been established. In all other radiating systems the exhausting mechanism will be ineffective.

Another object is to provide an exhausting mechanism consisting of a single hurling circuit divided into a plurality of independent branches, one for each radiating system.

s Another object is to provide an exhausting mechanism, comprising a supply tank,-a pump for withdrawing liquid from the tank and returning it thereto, and a plurality of independent jet exhausters through each 'of which liquid is forced V by the pump, there being a separate control valve for each exhauster for determining whether or not that particular exhauster shall be eifective.

Another object is to provide, in connection with an exhausting mechanismof the type last described, an automatic valve mechanism whereby the cut-ofl valve for each jet exhauster is opened or closed in accordance with the pressure differential existing in the radiating system with which that exhauster is connected.

Other objects and advantages of the invention will be more apparent from the following detailed description of one approved form of apparatus embodying the principles of this invention.

In the accompanying drawings:

' prises a pair of balanced valves for controlling the Fig. 1 is a diagrammatic elevation showing one form of the apparatus.

Fig. 2 is an elevation of the exhausting apparatus and the control valves therefor.

Fig. 3 is a plan view of the apparatus shown in Fig. 2.

Fig. 4 is a vertical section, on an enlarged scale, through one of the jet exhausters and cut-off valve therefor, the view being taken substantially on the line 4-4 of Fig. 2.

Fig. 5 is a vertical section through one of the differential control valves, or pilot valves.

In Fig. 1 is illustrated portions of a heating apparatus including three separate radiating systems adapted to operate simultaneously at the same or difierent sub-atmospheric pressures. It will be apparent as the description progresses that two or any greater number of such radiating systems could be operated in the same manner. The heating system comprises a single steam generator A, the three similar separate radiating systems indicated generally by the reference characters B, C, and D, and a single exhausting mechanism indicated generally at E.

The generator or boiler A, which may be of any approved form, furnishes steam to header 1, from which a drip-pipe 2 leads back to the lower portion of the boiler at 3. A normally closed drain connection for the system is indicated at 4.

Steam is delivered from the header 1 through supply mains 5, 5 and 5 to the respective radiating systems B, C, and D. The principal elements of each of these systems may be substantially identical, and only the system B is completely shown in Fig. 1. Such portions of the similar systems C and D as are shown are indicated by the same reference characters as, similar parts in the system B (which will now be described) with the exponent a and b respectively.

The radiating system B includes a main cutoff valve 6 which is normally open when the system is in operation. The reducingvalve '7 may be of a well known form, such as disclosed in the Dunham patent hereinabove referred to. It comflow of steam at boiler pressure into the relatively low pressure portion 8 of the supply main. The valves are controlled through stem 9 from a diaphragm located in casing 10, this diaphragm being subject on one side to atmospheric pressure and on the other side to the sub-atmospheric pressure existing in the portion 8 of supply main 5, this pressure being delivered through conduit 11 which connects with supply main 8 at some little distance from the reducing valve so as not to be influenced by the fluctuations in pressure within t e-valve chamber. A lever 12 fulcrumed at 13 and pivoted at 14 to the operating stem 9, supports from its ends the adjustable weights 15 and 16. By properly adjusting these weights a force is, exerted through lever 12 on stem 9 which either assists or opposes the pressure differential exerted on the diaphragm in casing 10. The resultant force applied to stem 9 either opens or closes the reducing valves. The weights 15 and 16 are so adjusted that when the desired vacuum or sub-atmospheric pressure is attained in the portion 8 of supply main 5, the diaphragm in casing 10 will be moved to close the valve and shut off the fiow of further steam into the supply main from header 1. As the steam in supply main 8 and the radiators supplied therefrom is condensed or otherwise dissipated, the pressure in the supply main will be lowered whereupon the diaphragm will be actuated in the opposite direction to open the valves and admit more steam to the supply main 8. This action will be substantially continuous so that the steam in supply main 8, (and consequently the radiators hereinafter described) can be maintained substantially con- ,stant at any subatmospheric pressure regardless of the pressure of the steamsupplied from generator A through header 1.

This sub-atmospheric pressure steam is delivered from supply main 8 to each radiator 1'7 through a steam riser 18 and a normally open inlet valve 19. a A steam trap 20 is interposed between the lower portion of radiator 17 and a return pipe 21 leading to the return main 22. The radiating system B may comprise any desired number of radiating units 1'7, in the example here shown two such radiating units being shown one of them being indicated by primed reference characters. When steam from radiator 17 enters the steam*trap 20 it will expand the operating means in this trap and close the valve to prevent the escape of steam into the return main. When suflicient air or condensate has accumulated, the valve operating means will be cooled and will contract to open the valve and permit the escape of the condensate and air through pipe 21 to the return main 22. The condensate which accumulates in supply main 8 is delivered through float and thermostatic trap 23 into return main 22. Return main 22 leads down to one of the exhausting ejectors of the vacuum-producing means E, as hereinafter described. An equalizing pipe 24 connects the return main 22 with the supply main 8, this pipe including a one-way valve 25 opening towards the supply main 8, and a normally open cut-off valve 26. The check valve 25 will normally be held closed by the higher pressure in the supply main, but will open if for any reason the pressure in the supply main should fall below the pressure in the return main so as to equalize the pressures in the two pipes. chambers 27 and 28 are conveniently located in the low and high pressure portions of equalizing pipe 24, and pressure control pipes 29 and 30 v extend respectively from these surge chambers to differential control mechanism 31. This differential pressure controller may be the same as that disclosed in the Dunham patent above referred to, or in the co-pending application of McMurrin, Serial No. 174,994, filed March 12, 1927. In general, this controller comprises a casing divided into two chambers by a flexible diaphragm. The two chambers are connected respectively with the supply and return sides of the heating system by pipe connections 30 and 29. A spring tends to urge the diaphragm in one direction, the action of the spring being balanced by the desired pressure diiferential between the supply and return sides of the system. When the pressure differential falls below the desired minimum, the spring will actuate the diaphragm and a stem projecting therefrom in one direction, thereby closing the switch 32, which through leads 33 controls the motor-starter 34. Power leads 35 lead 'to the motor 36 which operates the exhausting mechanism E hereinafter described. The wiring connections are merely shown diagrammatically in the drawings, and it is to be understood that a three-wire system, or any other desired type of wiring could be used. When the desired pressure differential has been attained, the diaphragm of the differential controller will overcome the spring and open switch 32, whereupon motor 36 and exhausting mechanism E are Surge again temporarily stopped. All of the above is substantially the same as in the Dunham patent hereinabove referred to.

It will be noted that each of the separate radiating systems B, C, and D has its own differential controller 31 and switch 32, from which leads 33 extend in parallel to the motor starter 84.v Whenever the pressure differential between the radiators and return main of any one of the radiating systems has fallen below thedesired minimum, the switch 32 of that circuit will be closed so as to complete the operating circuit of the starter 34, and the motor 36 will continue to operate as long as any one of the switches 32 is closed. The motor 36 will only be stopped when allof the switches 32 are open, that is when the desired pressure differential has been obtained in all of the separate radiating systems.

A centrifugal pump 37 driven by the motor 36 withdraws water'through pipe 38 from the tank 39 and projects this water upwardly into the manifold 40. From the manifold 40, this water may pass upwardly through any one or more of a plurality of ejector units hereinafter described in detail, all of these ejector units discharging into a manifold 41 from which the water is conducted back into the upper portion of tank 39. The air and liquid condensate withdrawn from the several radiating systems is also discharged through manifold 41 into tank 39, the air escaping through pipe 42 provided with the outwardly opening check valve 43. Since condensate is continually delivered to tank 39, the water level within this tank will gradually rise and when a certain level is reached the float 44 will, through lever and link connections 45 open the valve 46 in a discharge pipe 47 leading from the manifold 40. This pipe 4'1 is provided with a check valve 48 and cut-off valve 49, and leads into drip pipe 2 of the generator A. When the valve 46 is opened, pump 37 will force water through the pipe 47, past check valve 48 and thence back into the boiler or generator. When the water level within tank 39 has been suificiently lowered, the valve 46 will be closed by the downward movement of float 44.

A vertical section through one of the ejector units and the control valve therefor is shown in Fig. 4. The valvecasing 50 of the ejector cut-off valve 51 is mounted on the manifold 40 and has an inlet port 52 registering with a corresponding outlet port in the manifold. The outlet port 53 of valve 51 communicates with the ejector nozzle 54 mounted in the usual manner in the ejector suction chamber 55. The return main 22 of the radiating system leads through a strainer 22' and a check valve 56 (opening toward the ejector) into the'inlet port 57 of ejector chamber 55. The liquid stream forced through the ejector by pump 37 is projected through nozzle 54 into the outlet tube 58 leading through discharge chamber 59 'into the outlet manifold 41 and thence into tank 39. The condensate and air withdrawn from return main 22 into chamber are also carried along with the liquid stream discharged from nozzle 54 into the outlet tube 58 and thence into tank 39.

A web 60 within the valve chamber 50 separates the inlet port 52 from the outlet port 53, the valve opening in said web being closed by a movable valve 61 mounted on a valve stem 62 guided at one end in a slide bearing 63 formed in the cap 64 secured in one side of the valve chamber. The other end of valve stem 62 is secured to the central portion of a diaphragm 65 which is secured at its outer periphery about an opening in the valve casing by means of a diaphragm casing 66. A larger diaphragm 67 is secured at its outer edges to the casing 66 by means of a second diaphragm casing 68 which forms a diaphragm chamber 69 about the outer side of larger diaphragm 67. The chamber '70 between the diaphragms 65 and 67 is open to the atmosphere, through ports '71. The two diaphragms are centrally connected to operatev in unison by means of an extension 72 of the valve stem 62. An inlet pipe '73 and an outlet pipe 74 provides means for conducting a control pressure fluid, preferably water, into and out of the diaphragm chamber 69. An orifice plate 75 provided witha small central orifice '7 6 is mounted within the union '77 secured between serves to restrict the flow of water through outlet pipe 74 so that when water is forced into chamber 69 through inlet pipe 73, a relatively high pressure may be built up in the operating chamber 69.

It will be noted that the inner surfaces of valve 61 and diaphragm 65 are both subject to the pressure exerted by the pump 3'7. However, the outer face of valve 61 is normally subject to atmospheric pressure communicated through the ejector and conduits from the tank 39, and the outer face of diaphragm 65 is subject to atmospheric pressure existing in chamber 70. Since the effective area of diaphragm 65 is somewhat greater than the eilective area of valve 61, the pump pressure exerted on diaphragm 65 will normally serve to hold the valve 61 against its seat and shut off the flow of water through the valve 51. The diaphragm 67 has a greater area than diaphragm 65, and when a pressure greater than atmosphere is built up in the diaphragm chamber 69, this will overbalance the pressures on the smaller diaphragm 65 and serve to open the valve 61. At such times, water will flow freely through the valve 51 into and through the ejector nozzle 54 and this exhauster unit will then be operative to withdraw air and condensate from the return main 22 and carry same into the tank 39.

The admission of pressure fluid into the operating diaphragm chamber 69 is controlled by a differential-pressure pilot valve 78, shown in detail in Fig. 5. The valve casing '79 is provided with an inlet port 80 and an outlet port 81 separated by an internal web 82. A pair of valve openings in web 82 are closed by movable valves 83 and 84 mounted on valve stem 85 projecting upwardly through slide bearing 86 and stuffing box 87 in the upper portion of the valve casing. The stem 86 connects with the lower end of a yoke 88 through which extends laterally the lever 89 pivoted atone end 90 "in the supporting casing of the valve assembly 78. An adjustable weight 91 is mounted on the free end portion of lever 89. A suitable upward extension on the stem 86, indicated generally at 92, is connected with the central portion of an operating diaphragm 93. Suitable diaphragm casings 94 and 95 between which diaphragm 93 is mounted serve to'to form operating chambers at the two sides of the diaphragm 93. Portions of the walls of these chambers are formed by the two similar smaller diaphragms 96 and 97, each secured centrally to the valve stem 92. These smaller diaphragms serve to balance one another without disturbing the pressure differential, and avoid the use of stumng boxes about the valve stem. The outer surfaces on. the two smaller diaphragms are subject to atmospheric pressure exerted through the open casing '78 and the upper closure or cap 98 provided with open ports 99. A control pressure pipe 100, leading through pipe 29 to the low pressure side of the radiating system B, connects with the pressure chamber 101 above operating diaphragm 93. In a similar manner, a pipe 102 leading through pipe 30 to the relatively high pressure side of the radiating system communicates with the pressure chamber 103 below the diaphragm 93.

It will be apparent that the higher pressure existing in the chamber 103 beneath diaphragm 93 will normally serve to lift up on the valve stems 92 and 86 and hold the valves 83 and 84 in closed position so as to shut off the flow of fluid thriugh valve casing '79. This force is opposed by the adjustable weight 91, and when the pressure differential has fallen below the desired minimum, the weight 91 will overcome this pressure difference and open the valves 83 and 84.

It will be understood that there are similar pilot valves '78 and 78? for the other two radiating systems C and D respectively, these pilot valves being similarly connected with the high and low pressure sides of these respective systems. fold and has branches 105 leading to the inlet ports 80 of the respective pilot valves 78. The pipe 73 leads from the outlet port 81 of the pilot valve to the operating pressure chamber 69 of the corresponding control valve 51. The outlet pipes '74 from the several pressure chambers 69, all connect with a pipe 106 discharging into the tank 39.

In the general operation of this heating system, each of the separate radiating systems B, C, and. D, will operate, independently, substantially as set forth in the Dunham patent, hereinabove referred to. The reducing valve 7 in each system will be set so as to deliver steam at any desired sub-atmospheric pressure to the radiators in that system. All of the systems may be set to use steam at the same pressure, and temperature, or one of the systems (for example the system B) may have its reducing valve 7 set so as to use steam at a relatively high sub-atmospheric pressure, whereas one of the other systems, such as C, may have its reducing valve set so as to use steam at a much lower sub-atmospheric pressure. In the example just given, that portion of the building in which system B is located would require a greater amount of heat to maintain it at the proper temperature than the portion of the building heated by the system C. The exhausting mechanism will function until the return mains 22 of each system have been exhausted to the point where the desired pressure differential has been established between the supply and return sides of the system. "At

such times, all of the differential pressure controllers will operate to open all of the switches 32, thus stopping the motor 36 and consequently stopping the operation of the pump 37 and of the entire exhausting system. In case the pressure differential in any one of the radiating systems falls below the desired minimum, the corresponding switch 32 will be closed and the motor 36 will be started to cause pump 37 to force liquid from tank 39 through the hurling circuit and back into the tank. At the same time the corresponding difl'erential pressure pilot valve 78 (which it will be noted is connected in parallel with the differential pressure controller 31 of that system), will operate to open the corresponding valve '79 and permit water under pressure A liquid conduit 104 leads from the mani-' to be forced from manifold 40 through pipes 104 and 105, valve '79,.and pipe 73, into the pressure chamber 69 of the valve 51 corresponding to that radiating system. The orifice plate in the outlet pipe 74 will prevent the operating liquid from flowing out of chamber 69 as fast as it is forced in so that a pressure will be built up in chamber 69 forcing the diaphragm 67 in a direction to open the valve 61 andhold this valve in open position as long as the pressure is maintained in chamber 69. With the valve 61 open, water will be forced from manifold 40 through valve 51 and ejector nozzle 54, thus causing gas and condensate to be withdrawn from the return main 22 of the particular radiating system now under consideration. The water and air will be discharged into the tank 39, from which the air escapes through pipe 42 and the water is forced at intervals back to the generator A, all as described hereinabove. During the operations just described, in any one or more of I the other radiating systems where the desired pressure differential is still established, the corresponding cut-off valve 51 will be maintained closed and the corresponding ejector unit will be inoperative.

When the necessary pressure differential has again been established in the system just under consideration, the corresponding pilot valve '78 will operate to close the valve 79 and cut off the flow of water under pressure to the diaphragm chamber 69. The pressure in this chamber will be dissipated through the orifice plate 75 in outlet pipe 74, and the pump pressure on diaphragm 65 will operate to close the valve 61 and cut off the flow of 'water through the ejector. The differential pressure controller 31 will also be operated to open the switch 32 thus stopping the pump motor 36 in case this radiating unit was the only one requiring the operation of the exhauster at this time. However, if one of the other systems has fallen below the desired pressure difierential, the switch 32 of that system will remain closed so that the motor will not cease to operate.

It will now be apparent that the operation of this heating system is substantially the same as that set forth in the Dunham patent hereinabove referred to, with the exception that a plurality of independently controlled and adjusted radiating systems are all supplied with steam from the same generator, and a single exhausting mechanism is used to establish and maintain the desired vacuums in all of the systems and to return the condensate from all of the systems to the common generator. The exhausting mechanism will function only when its services are necessary to maintain the necessary pressure differential in any one or more of the systems. At other times it will be idle, and at no time will it operate on any system other than the system or systems in which the pressure differential has fallen below the desired minimum. The operation of the exhausting mechanism is entirely automatic at all times.

While three independent branches of the heat- ,ing system have been shown by way of example,

it will now be apparent that any desired number of such systems could be used by an obvious duplication of the exhausting units hereinabove described. In other words, the exhausting mechanism will be provided with an ejector and control mechanism therefor for each separate radiating system, all of the ejectors being fed from the common manifold 40 and discharging through 1 the manifold 41 back to the tank 39.

While in the structure here shown by way of example, a differential controller 31 has been utilized to operate switch 32 and a separate differential controller 78 is utilized to operate the pilot valve 79, it will be apparent that these two controllers are connected in parallel and operate in unison so that a single controller could be used to operate both the switch and the pilot valve.-

Furthermore, in some installations the motor 36 and pumping means driven thereby might be 1. In combination with a vacuum producing element, pumping mechanism for forcing an actuating liquid through the exhausting element, a diaphragm operated valve for controlling the flow of liquid to the element, a conduit-for conducting fluid under pressure from the pumping mechanism to the valve-operating diaphragm, a pilot valve in this conduit, and means controlled by pressure changes in the space exhausted by the element for operating the pilot valve.

2. An exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces comprising a hurling circuit including a separating tank, a pump adapted to propel liquid through the circuit, and a plurality of ejector units arranged in parallel branches of the hurling circuit, each ejector being in operative connection with one of the spaces to be evacuated, a cutoff valve controlling the flow of liquid through each branch of the hurling circuit, pressure-operated means for moving this valve, a conduit for leading liquid under pressure from the pump to the pressure operated means, a pilot valve in said conduit, and means for operating said pilot valve in response to pressure changes in the space to be evacuated.

3. An exhausting mechanism comprising the combination with a pump, means for driving the pump, a separating tank, an inlet manifold, conduits through which the pump forces liquid from the tank into the manifold,.an outlet manifold discharging back into the tank, a plurality of exhauster units arranged in parallel between the inlet and outlet manifolds, each unit comprising an ejector for withdrawing fluids from a space and discharging them into the separating tank, a cutoff valve for controlling the flow of liquid from the inlet manifold to the ejector, pressure operated means for opening and closing the cutoff valve, a conduit for delivering liquid under pres-- sure frointhe pump to this pressure operated means, a pilot valve in this latter conduit, and a differential pressure controller for opening and closing the pilot valve.

4. An exhausting mechanism comprising the combination with a pump, a motor for driving the pump, a separating tank, an inlet manifold,

conduits through which the, pump forces liquid from the tank into the manifold, an outlet manifold discharging back into the tank, a plurality of exhauster units arranged in parallel between the inlet and outlet manifolds, each unit coma space and discharging them into thetank, a cutofi valve for controlling the flow of liquid from the inlet manifold to the, ejector, pressure operated means for opening and closing the cutoff valve, a conduit for delivering liquid under pressure from the pump to the pressure operated means, a pilot valve in this conduit, and means controlled by variations in a pressure-differential maintained by the ejector for governing the operation of the motor and pilot valve.

5. An exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces, comprising a hurling circuit including a separating tank, a pump adapted to propel liquid from the .tank through the circuit and back into the tank along with fluids exhausted from the spaces, and a plurality of ejector units arranged in parallel branches of the hurling circuit, each ejector being in operative connection with one of the spaces to be evacuated, and automatically acting means for separately and independently cutting each ejector into or out of the hurling circuit in accordance with pressure changes in the space evacuated by that particular ejector.

6. An exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces, comprising a hurling circuit including a separating tank, a pufnp adapted to propel liquid from the tank through the circuit and back into the tank along with fluids exhausted from the spaces, and a plurality of ejector units arranged in parallel branches of the hurling circuit, each ejector being in operative connection with one of the spaces to be evacuated, automatically actingmeans for separately and independently cutting each ejector into or out of the hurling circuit in accordance with pressure changes in the space evacuated by that particular ejector, a motor for driving the pump, and means for automatically starting the motor when any one of the ejectors is connected in the hurling circuit and for stopping the pump when all of the ejectors are cut out of the hurling circuit 7. An exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces, each having supply and return conduits, comprising a hurling circuit including a separating tank, a pump adapted to propel liquid from the tank through the circuit and back into the tank along with fluids exhausted from return conduits, a motor for driving the pump, and a plurality of jet exhausters arranged in parallel branches of the hurling circuit, each exhauster being in operative connection with a return conduit leading from one of the spaces to be evacuated, and automatically acting means for separately and independently cutting each ejector into or out of the hurling circuit in response to changes in the pressure differential between the supply and return conduits of the space exhausted by that ejector;

8. An exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces, each having supply and return conduits, comprising a hurling circuit including a separating tank, a pump adapted to propel liquid from the tank through the circuit and back into the tank along with fluids exhausted from the spaces through the return conduits, a motor for driving the pump, and a plurality of jet exhausters arranged in prising an ejector for withdrawing fluids from the spaces through the parallel branches of the hurlifig circuit, each exhauster being in operative connection with a return conduit leading from one of the spaces to be evacuated, automatically acting means for separately and independently cutting each ejector into or out of the hurling circuit in response to changes in the pressure differential between the supply and return conduits of the space exhausted by that ejector, and means for automatically starting the motor when any one of the ejectors is connected in the hurling circuit and for stopping the motor when all of the ejectors are cut out of the hurling circuit.

9. An exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces, each having supply and return conduits, comprising a hurling circuit including a separating tank, a pump adapted to propel liquid from the tank through the circuit and back into the tank along with fluids exhausted from the spaces through the return conduits, a motor for driving the pump, and a plurality of jet exhausters arranged in parallel branches of the hurling circuit, each exhauster being in operative connection wi h a:

return conduit leading from one of the s aces to be evacuated, a plurality of cut-oif valves, one for each exhauster for controlling the flow of liquid through each branch of the hurling circuit, and means for automatically and separately opening or closing each valve in response to changes in the pressure difierential between the supply and return conduits of the space exhausted by that ejector.

10. An exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces, each having supply and return conduits, comprising a hurling circuit including a separating tank, a pump adapted to propel liquid from the tank through the'circuit and back into the tank along with fluids exhausted from the spaces through the return conduits, a motor for driving the pump, and a plurality of jet exhausters arranged in parallel branches of the hurling circuit, each exhauster being in operative connection with a return conduit leading from one of the spaces to be evacuated, a cut-ofi valve for controlling the flow of liquid through each branch of the hurling circuit, means for automatically opening or closing this valve in response to changes in the pressure diiferential between the supply and return conduits of the space exhausted by that ejector,- and means for automatically starting the motor when any one of the ejectors is connected in the hurling circuit and for stopping the motor when all of the ejectors are cut out of the hurling circuit.

11. Am exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces, comprising a pump, a plurality of vacuum producing elements actuated by the pump, each vacuum producing element being in operative connection with one of the spaces to be evacuated, and automatically acting means for separately and independently placing these elements into or out of operation in accordance with pressure changes in the respective spaces exhausted by each element.

12. An exhausting mechanism adapted to simultaneously but independently evacuate one or more of a plurality of separate spaces, comprising a pump, a plurality of ejectors through which an actuating fluid is forced by the pump,

each ejector being in operative connection with one of the spaces to be evacuated, and means for separately and independently controlling the fiotv of fluid through each ejector in accordance with pressure changes in the respective space the vacuum producing elements is in operation,

and means for stopping the pump when all of the vacuum producing elements are out of operation.

14. In a steam heating system, a source of steam, a plurality of separate radiating systems, means for supplying steam from the source to each of these systems, each system comprising a radiator, means for maintaining the steam in the radiator at any desired sub-atmospheric pressure, a steam trap at the outlet of the radiator and a return main for exhausting air and condensate from the radiator, and a single exhausting mechanism comprising a plurality of independently operable vacuum producing elements, one for each radiating system, and means operated by variations in the pressure difierential between the supply and return sides of each system for determining the operativeness of the corresponding vacuum producing element.

15. In a steam heating system, a source of steam, a plurality of separate radiating systems, means for supplying steam from the source to each of these systems, each system comprising a radiator, means for maintaining the steam in the radiator at any desired sub-atmospheric pressure, a steam trap at the outlet of the radiator and a return main for exhausting air and convdensate from the radiator, and a single exhausting mechanism comprising a single pumping mechanism, a plurality of independently operable ejectors supplied with fluid from the pump, a motor for driving the pump, and means operated by variations in the pressure diiferential between the supply and return sides of each radiating system for determining the operativeness of the corresponding ejector and for starting'and stopping the motor.

16. In a steam heating apparatus, a source of steam, a plurality of separate radiating systems, means for supplying steam from the source to each of these systems, each system comprising a radiator, means for determining. the sub-atmospheric pressure of the steam in the radiator, a steam trap at the outlet of the radiator, and a return main for exhausting air and condensate from the radiator,,and an exhausting mechanism comprising a tank, a hurling circuit for withdrawing liquid from the tank and returning it thereto, the circuit including a pump, a motor for driving the pump, and a plurality of ex- -flow of liquid through that branch of the hurling circuit, and a differential controller for closing the valve when a desired pressure difierential has been established between the radiator and return main in that system.

17. In a steam heating apparatus, a source of steam, a plurality of separate radiating systems, means for supplying steam from the source to each of these systems, each system comprising a radiator, means for determining the sub-atmospheric pressure of the steam in the radiator, a steam trap at the outlet of the radiator, and a return main for exhausting air and condensate from the radiator, and an exhausting mechanism comprising a tank, a hurling circuit for withdrawing liquid from the tank and returning it thereto, the circuit including a pump, a motor for driving the pump, and a plurality of exhausting units one for each radiating system arranged in parallel in the hurling circuit, each unit comprising an ejector with the intake of which the return main of the radiating system is connected, a cutoff valve for controlling the flow of liquid through that branch of the hurling circuit, and means in each radiating system operated by the pressure differential existing in that system for operating the cutoff valve and stopping or starting the motor. a

18. In a steam heating apparatus, a source of steam, a plurality of separate radiating systems, means for supplying steam from the source to each .of these systems, each system comprising a radiator, means for determining the sub-atmospheric pressure of the steam in the radiator, a. steam trap at the outlet of the radiator, and a return main for exhausting air and condensate from the radiator, an exhausting mechanism comprising a tank, a hurling circuit for withdrawing liquid from the tank and returning it thereto, the circuit including a pump, a motor for driving the pump, and a plurality of exhausting units one for each radiating system arranged in parallel in the hurling circuit, each unit comprising an ejector with the intake of which the return main of the radiating system is connected, a cutofi valve for controlling the flow of liquid through that branch of the hurling circuit, a pair of pressure operated controllers in each radiating system operated by the pressure differential existing between the supply and return sides of the system,,one of the controllers opening and closing the cutofi valve, and a switch operated by the other controller for stopping and starting the motor.

JOHN H. VAN ZANDT. 

